1. Field of the Invention
The present invention generally relates to analog-to-digital converters and it particularly relates to an analog-to-digital converter in which the input analog signal is compared with a reference signal by a plurality of comparators provided in parallel.
2. Description of the Related Art
As an example of a circuit for converting the inputted analog signals into the digital signals, there is available a pipeline-type A-D converter. A pipeline-type A-D converter is configured such that sub-A-D converters of low bits are connected in a plurality of stages. The inputted analog signal is A-D converted in stages through the respective sub-A-D converters. Each sub-A-D converter is provided with a plurality of comparators, and each comparator compares the inputted analog signal with the reference voltage so as to convert the analog signal into the digital signals.
The digital signals obtained after the input analog signal has been compared with the reference voltage are converted to the binary codes by the encoder. The structure of the encoder is determined according to the number of bits used to represent the binary code to be produced. In other words, if the numbers of bits in the binary code to be produced differ, the structure of the encoders will also differ. Thus, even if a circuit that compares an input analog signal with a reference voltage is shared when two binary codes having different numbers of bits are generated, two encoders need to be provided. This inhibits the reduction in circuit scale of an analog-to-digital converter.